Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 201728
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1228 PM CDT Mon Mar 20 2017

.DISCUSSION...Updated for latest aviation discussion below.

&&

.AVIATION...VFR expected to continue for the next 24 hours with a
very dry atmosphere in place. (12Z BRO sounding measured 0.62" of
precipitable water, which is in the lowest 10th percentile for
this date.) This morning`s flat Cu field is already mixing out,
per visible satellite imagery. SSE breezes have kicked in just a
bit stronger than forecast and will continue through around
sunset. Patchy fog may form over the Northern Ranchlands late
tonight but is not expected to affect the RGV terminals as wind
speeds stay up in the 8-10KT range. More of the same in store
tomorrow, with SSE winds picking up by mid-late morning and
perhaps some high clouds streaming by.

&&

.PREV DISCUSSION... /issued 929 AM CDT Mon Mar 20 2017/

DISCUSSION...Updated for latest marine discussion below.

MARINE...Quick update to lower wave heights for the outer Gulf
waters through 06Z tonight as seas are down to 2.3 feet at Buoy
020 and 2.7 feet at TABS-K buoy. Better matched with neighbors now
as well. Updated Coastal Waters Forecast will be out shortly.

PREV DISCUSSION... /issued 635 AM CDT Mon Mar 20 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Mostly clear skies and light southeast winds prevail
across portions of Deep South Texas this morning. Some patchy fog
and low ceilings have developed across the northern ranchlands
overnight but should remain north of Valley airports. Otherwise, VFR
conditions expected today as surface winds once again becomes
breezy due to the interaction of high pressure over the Gulf and
low pressure across west Texas. Southeast winds will gradually
diminish after sunset this evening with patchy fog possible north
of TAF sites overnight.

PREV DISCUSSION... /issued 427 AM CDT Mon Mar 20 2017/

SHORT TERM (Today through Tuesday): High presssure at the surface and
aloft will maintain warm and dry conditions across Deep South Texas
through the short-term. Light winds and cooler temperatures have
allowed some fog to develop across portions of Brooks and Jim Hogg
counties this morning. The fog will lift and mix out by mid-morning
as winds begin to increase.

Very dry air (especially above 925 mb) will mix down today with
dewpoints away from the coast dropping into the 50s. The interaction
of surface high pressure over the Gulf and lower pressure across
west Texas will support breezy southeast today. High temperatures
today will be in upper 80s to lower 90s (except for the low to mid
80s near the coast) due to combination of abundant sunshine and a
drier airmass in place. Southeast winds will gradually diminish
after sunset this evening. Low temperatures tonight will be in the
60s across most of the area under partly cloudy skies. Patchy fog
will be possible again tonight across portions of the northern
ranchlands. Tuesday will be a repeat of today with plenty of
sunshine and high temperatures in the upper 80s to lower 90s across
much of the area. Breezy southeast winds will develop again on
Tuesday due to the tight pressure gradient.

LONG TERM (Tuesday Night through Sunday): 500 mb ridging will
prevail over the RGV from Tues Night into Wed Night. A strong 500
mb closed low will then push across the south central Plains
states on Thurs and Fri. This will push a very weak cold front
through the region on Sat with little or now CAA expected Sat. A
SE flow will then quickly return Sat Night into Sun. Another 500
mb closed low will then move quickly in behind the first closed
low pushing over the central Plains states on Sun. Overall
moisture advection ahead of these 500 mb closed lows remain very
marginal through Sun. So will maintain only some slgt chc pops
with the passage of the closed low on Fri.

The PGF will be strongest on Thurs for the RGV ahead of the
surface low developing over the central Plains states. This will
result in breezy/windy conditions later in the week.

There is decent agreement between the GFS and the ECMWF in the
handling of this synoptic situation. The ECMWF is going with a
little warmer solution versus the GFS and prefer the ECMWF
solution for temps as believe that the cooler temps shown by the
GFS are a bit overdone.

MARINE (Now through Tuesday): Buoy 42020 reported south-southeast
winds around 14 knots with gusts near 16 knots and seas of 3 feet
with a period of 7 seconds at 03 CDT/08 UTC. Small craft should
exercise caution on the Laguna Madre today and Tuesday due to
moderate winds. The pressure gradient will begin to tighten tonight
and Tuesday, which may allow winds to reach SCEC criteria on the
Gulf waters by Tuesday afternoon.

Tuesday Night through Friday Night: With the PGF strengthening due
to the approach of the 500 mb closed low and the associated
surface low the south to southeast low level flow will steadily
increase through the latter half of the week. The best chances for
SCA conditions will range from Thurs through Fri Night mainly for
the lower Texas Gulf waters.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

53-Schroeder...Aviation/59



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